Production of aromatic hydrocarbons



Patented May 23, 1944 UNITED s'mras- PATENT. OFFICE PRODUCTION OF mace This invention relates to the manufacture of a new aromatic hydrocarbon. This hydrocarbon is produced as a by-product in the method described in my copending application, Serial No. 363,382, filed on October 29, 1940, for the production of aromatic hydrocarbons, this application hereinafter being referred to as the main application.

The process of the main application consists in the conversion, by catalytic cracking of allphatic or hydro-aromatic mineral oils. more especially those of medium boiling range (NO-400 0.), into a liquid mixture of completely aromatic substances, notably in such of lower boiling point than the original oil.

The object of the present invention is to provide new aromatic hydrocarbons.

The invention consists in new aromatic hydrocarbon which may be obtained from the opera tion of the process of the main patent and has the structural formula 1.2-(2'.1'-naphtho)-7.8- benzo-phenanthrene and the graphical formula and may be isolated from the fraction boiling between 250 and 270 C. under 1 millimetre pressure and has a melting point of 288 C., forming golden leaflets after recrystallisation from butyl acetate.

The invention also consists in improvements in and relating to the production of aromatic hydrocarbons substantially as herein described.

As regards the process in general, the following epitome may enable it easily to be followed without reference to the main specification.

(l) The process is a cracking process in presence of metallic catalysts. In order to define more clearly the nature of the catalytically active metals, it may be said that this group comprises all the metals apt to catalyse hydrogenation and dehydrogenation reactions. Such metals as the alkali metals, magnesium, aluminium or the like ARBONS Charles Weizmann, London, England No Drawing. Application October 14, 1941, Serial No. 414,981. In Great Britain May 20,1940 5 Claims. (Cl. 260-668) AROMATIC are excluded by the given definition. The metals are preferably used in such a form as to provide a large catalytic surface; they may be applied in compact or finely divided form, or deposited on suitable carriers, such as pumice or bentonitc, which by themselves do not exert the desired catalytic action. Single metals may be'used, or mechanical mixtures or alloys of two or more metals.

The metals which are mainly suitable for commercial work are iron, copper, nickel, cobalt, silver, chromium, molybdenum, tungsten, manganese. Of these I prefer copper or nickel. A mixture of two metals, such as copper and iron, has in many cases proved definitely superior to any of the constituents, separately.

(2) Temperature.-For a complete aromatisation, I found the temperaturebetween 630 and 700 C. necessary, the optimum temperature varying somewhat with the type of oil to be processed. At lower temperatures, the aromatisation by single throughput is only partial. If it is desired to complete it under these circumstances it is necessary to recycle the product with or without previous isolation of the aromatised part by suitable means, such as selective solvents, adsorption and the like.

(3) Pressure.-The process does not require high pressure; it is preferably carried out at a pressure closely approximating to that of the atmosphere.

(4) Liquid products.-The liquid product of the process consists practically entirely of arcmatic hydrocarbons, the purity of which has been established by means of ultraviolet'spectrography. The cuts are, therefore, extremely sharp.

The composition of the liquid products is practically independent of the nature and properties of the starting material.

The following figures, which are all by weight and calculated on the original oil subject to a tolerance of :2% give the composition of the products for a temperature between 630 and 700 0.:

The above products are associated with higher I fractions from which new aromatic hydrocarbons have been isolated. Of these one characteristic product according to the present application is a hydrocarbon, M. P. 288, forming golden leaflets after recrystallisation from butyl acetate.

(6) Startinomateriala-Ewry mineral oil or fraction of such can be used for the process, the results not being materially dependent on the starting material. They all are preferably preheated before being processed, but it is preferable to carry out this pre-heating at a temperature not high enough to cause a thermal cracking. If all the specified conditions are observed, the process is not accompanied by carbonisation. This is set out in greater detail in the following paragraph. It must, however, be stated that very high boiling fractions or fractions relatively poor in hydrogen do not'exhibit the same favourable behaviour. Its cracking is always accompanied with a certain amount of carbonisation.

(7) Lifetime of the catalyst-As the catalyst does not cause carbonisation of the mineral oil and the sulphur and nitrogen of this oil are converted into hydrogen sulphide and ammonia, re-

spectively, the catalyst has a practically unlimited lifetime.

The following example illustrates how the invention may be carried into effect:

Example In a steel tube, 2.10 m. in length and 7 cm. in diameter, 800 gms. of a catalyst consisting of four parts iron filings and one part copper fillings is placed. After oxidation by a stream of air at 450, and successively then reduced by hydrogen at 250 C., the catalyst was heated to 700, Vaseline oil was then passed over the catalyst at a speed of 800 gms. per hour. As a result 200 litres of gaseous products and 420 gms. of a liquid, darkbrown product was obtained per kilogram of Vaseline oil. Upon distillation of the liquid product. after a small head fraction, 221 gms. distilled between 75' and 180 and were entirely composed of aromatic hydrocarbons. Continuing the distillation in a vacuum of 10 mm. of mercury between 80 and 190, 133 gms. of a product which crystallised immediately and consisted of polycyclic, entirely aromatic hydrocarbons were ob tained.' The residue, weighing 66 gms. was a brownish-black tar, which distils only in a very high vacuum and contains still higher aromatic hydrocarbons.

It is from this tar that the new product as indicated above may be obtained.

with concentrated sulphuric acid (like chrysoquinone) and this fact as well as the solubility in aqueous sodium bisulphite solution made it highly probable that the hydrocarbon is a phenanthrene.

not an'anthracene derivative. These facts in conjunction with the following synthesis led to the The tar is fractionated under very reduced pressure, for example, 1 millimetre and the fractionboiling between 250 C. and 270 C. is isolated. It forms a viscous oil which solidifies partly on trituration with a mixture of light petroleum and acetone. The solid material is a new hydrocarbon thus obtained in a fairly pure state. It can be conveniently purified by recrystallisation I from butyl acetate, butyl alcohol or xylene.

The product is a hydrocarbon, M. P. 288, forming golden leaflets. This substance is obtainable with the process of the main application from any starting material.

Analysis and 'molecular weight determination 5 (Found:' C, 94.0; H. 5.9; mol. wt. 313. Calc. for CaeHis: C, 94.1; H, 5.9; mol. wt. 328) pointed to the composition CaeHm; a hydrocarbon of this empirical formula and the same melting point had been described before by J. W. Cook. (J. W. Cook, J. Chem. Soc. 1931, 506) from the synthetic method which served for its preparation, the

structure I of 1.Z-benzo 5.6-naphtho-anthracene had been derived.

Formula II' of a dibenzo-chrysene (1.2-2'.1'-

naphtho) -7.8-benzo-phenanthrene) for the hydrocarbon and to Formula III for the diquinone:

III

It had been observed that recycling of the fraction, boiling range 145-190", obtained in the aromatisation process of the main application at 600 C. results, inter alia, in a surprisingly high yield of chrysene (43% of this high fraction and 14.6% of the total charge). This was first tenta tlvely ascribed to the presence in this fraction of indene and/or alkyl-benzenes containing three carbon atoms in a straight chain (alkyl-benzene.

Comparison of the earlier with the later hydropropyl-benzene, propenyl-benzene). The formation of chrysene when in dene is passed through a red-hot tube. was known for many years past. (Spilker, Ber. Dtsch. Chem. Gas. 26, 1644 (1893) As this reaction involves the opening of the iive-membered ring, it I not been identified. Allyl-benzene gives in addition to the formation of chrysene, two side-reactions, viz. the isomerisation into propenyl-benzene (B. P. 175 C.)

and the degradation into toluene according to one or the other of the following two equations:

The presence of propenyl-benzene together with toluene and unchanged allyl-benzene, in th reaction product has been detected by determination of the boiling curve at a very eflicient column;

the above triadic isomerisation parallels similar reactions known, e. g. the isomerisation of allylnaphthalene into l-propenyl-naphthalene at 300 tion of allyl bromide (60 g.) and the Grignard compound, formed from magnesium (13 g.) and e-bromo-naphthalene ('14 g.). It formed a slightly yellowish liquid of B. P. .135-136/ 14 mm.; yield 97% (58 g.).

on passing it over a catalyst of the kind stated above at 659 C. a heavy tar was obtained which by trituration with ether could be separated into a liquid and a solid product. The melting point of the brown solid product could be raised by successive recrystallisation from ethyl butyrate, butyl alcohol and xylene, to 2'70? C. and showed in this stage no depression, on admixture of the "golden leaflets" (M. P. 288). From the solid part, a pure product was obtained by distillation in vacuo (12 mm.) and subsequent recrystallisation from ethyl butyrate, and was then in every respect identical with the "golden leaflets."

The liquid part of the reaction product consisted of naphthalene and a-methyl-naphthalene subjected to a iractionationin vacuo; it consisted entirely of naphthalene, B. P. 98-l()2/12 mm, M. P. 80, and l-methyl-naphthalene, B. P. 130- l35/12 mm., which was'identified by its characteristic picrate, M. P. 141 from alcohol. Care was taken to find whether any fl-derivative of naphthalene had been formed, viz. the hitherto unknown i-allyl-naphthalene or2'-methyl-naph thalene (picrate, M. P. 116). A migration of the ally] group into the 2-position before the desired reaction which would be parallel to the well-known thermal isomerisation of 3- into z-phenyl-indene (J. v. Braun and Manz, Ber. Dtsch. Chem. Ges. 62, 1059 (1929). Compare Blum-Bergmann, ibid. 65, 109, (1932).) would i have meant that the hydrocarbon Cam; could in presence of aluminium chloride, (Levina,

Karelova and Eliyashberg, Chem. Abstracts, 33, 2479 (1941).) or more closely the well-studded isomerisation of 1- into Z-butene in presence of metallic catalysts.

If Formula, II for the golden leaflets" were correct, it could be assumed that the hydrocarbon is formed in the course of the process of the main application by dimerising isomerisatlon from a naphthalene derivative, with an annexed cyclopenteno-ring or with a side-chain containing three carbon atoms, and it was further to be expected that lallyl-naphthalene, in contact with the catalyst of the main application, should be transformed into the-new hydrocarbon CzoHici of the "golden leaflets."

l-allyl-naphthalene was prepared by interachave the structures IV. V and VI instead of I.

Neither Z-methylnor z-allyl-naphthalene, however, are present in the reaction product which again supports the view that the "golden leaflets," obtained both in the Weizmann process and by thermal conversion of .i-allyl-naphthalene, are correctly represented by Formula I. The reaction product is also free from l-propenyl-naphthalene (picrate, M. P. 111) and oi the two cyclopenteno-naphthalenes (4.5-benzohydrindene', picrate M. P. 108 (Chem. Abstracts- The invention extends to this body produced by any process and also to derivatives of this new aromatic hydrocarbon.

I claim: 1. As a new product, the hydrocarbon 1.2- (2'.1'-naphtho) -"l.8-benzo-phenanthrene, having the structural formula:

said hydrocarbon having a, melting point of about 288 C. and crystallizing in golden-leaflets.

2. The process of manufacturing the hydrocarbon 1.2-(2'.1-'-naphtho)-7.8-benzo-phenanthrene which comprises passing a mineral oil in contact with a hydrogenating-dehydrogenating catalyst having a large surface area heated within the temperature range of about 630-700" C. at substantially atmospheric pressure, fractionating the resulting products, recovering a fraction boiling within the range of about 250-270" C. under a pressure of about 1 millimeter or mercury and isolating said hydrocarbon from said fraction.

3. The process of claim 2 wherein said catalyst is a finely divided metal, selected from the group consisting oi. hydrogenation and dehydrogenation catalysts.

4. The process of claim 2 wherein said catalyst is a finely divided mixture of metals, selected from the group consisting of hydrogenation and dehydrogenation catalysts.

5. The process 01 claim 2 wherein said catalyst is a finely divided alloy of metals, selected from the group consisting oi hydrogenation and dehydrogenation catalysts.

CHARLES WEIZMANN. 

